In flexible tube bagging machines the shaping member effects the deformation of a flat foil, which is pulled off from a roll, to a tubular formation. The edges of the foil are hereby overlapped and are connected to one another, after passage of the shaping member at the overlapping points, by welding, sealing or gluing, after which an all around sealed tube is produced, which is divided into individual bags through transverse seams.
Known shaping members are constructed symmetrically, namely the collar chest portions are substantially of equal length and converge toward the center plane of the shaping member. Center plane is here the plane, which extends through the axis of the sleeve portion and the center of the collar neck portion. As a rule the axis of the sleeve portion extends perpendicularly and the mentioned center plane is positioned at a right angle to the front side of the machine. With this also overlapping of the foil edges approximately in the center plane takes place. The constructively favorable arrangement of transverse sealing jaws, with which transverse seams for forming of bags are produced, is the arrangement which is parallel to the front side of the machine. In this common arrangement, longitudinal seams are obtained with the known shaping members at one flat side of the finished bag. The position of the longitudinal seam is advantageous in the case of a flat bag and also does not interfere.
In the case of some bag forms, so in particular in the case of square bags which can stand, it is desired that the longitudinal seam does not extend in the area of a flat side, because this is not advantageous for the appearance of the bag and because the pressure of longitudinal sealing jaws on the flat side of a fill pipe is problematic. A flat sidewall of a fill pipe has in comparison with a pipe the wall of which is arced, for example a pipe having a circular cross section, only a small rigidity. These disadvantages are avoided when the longitudinal seams are moved into the area of a bag edge, because a longitudinal sealing jaw can then be engaged in the vicinity of an edge of the fill pipe and thus find a stiff abutment.
Such a position of the longitudinal welding seam has been achieved up to now by either arranging the transverse sealing jaws which act as the foil transfer tongs suitably staggered or by supplying the foil, generally also called wrapping material, from the side. Both require special machine constructions, which are substantially more expensive than standard flexible tube bagging machines, in which the wrapping material is supplied from the backside of the machine and the transverse sealing jaws are aligned parallel to the front side of the machine.
The basic purpose of the invention is to construct a flexible tube bagging machine of the above-mentioned type so that also in the case of the mentioned standard arrangement the longitudinal seam of the bags can be moved from the mentioned center plane into the vicinity of a bag edge.
This purpose is attained according to the invention by the collar chest parts being of different length and the longer collar chest portion being guided beyond the center plane of the shaping member, which extends through the longitudinal axis of the sleeve portion and the center of the collar neck portion.
In the case of a flexible tube bagging machine which is constructed in the above manner, in spite of supplying the wrapping material from the backside of the machine and in spite of the arrangement of the shaping member such that its collar chest portions rest on the front side of the machine, it is achieved that overlapping of the foil edges is moved far from the mentioned center plane. It is therefore easily possible, in the case of a for example square bag to move the longitudinal seal into the area of the bag edge. Therefore, it is possible with the aid of the invention to maintain the structurally particularly advantageous standard arrangement in which the transverse sealing jaws extend parallel to the front side of the machine and the wrapping material is supplied from behind. Such a machine is substantially more advantageous than special constructions having tong transfer devices and the transverse sealing jaws are rotated from the front plane of the machine or as machines having a lateral feed of the wrapping material. It is possible to use, even when a lateral arrangement of the longitudinal seam is desired, basic forms of machines which are produced in series and which differ substantially only in using an inventive asymmetric shaping member from standard machines.
As can be seen from the above discussions, the invention is particularly advantageous, when the fill pipe of the flexible tube bagging machine and thus also the sleeve portion have a nonround cross section. In particular the embodiment wherein the sleeve portion has a rectangular cross section is particularly of a great importance because with it square-shaped bags can be manufactured, in which the longitudinal seal extends in the area of a bag edge. The bags can also have large-surface sidewalls, since the flexibility of a plane fill pipe wall is no longer disadvantageous, because the contact pressure of the longitudinal sealing jaw occurs in the area of a stiff side edge of the fill pipe.
The collar neck portion is preferably also constructed asymmetrically. This is advantageous because a larger portion of the width of the wrapping material strip must be pulled to the longer collar chest portion than to the shorter collar chest portion.